The present invention relates to a glow plug for internal-combustion engines, the glow plug being known from the document DE-A-2637464. This document describes a plug comprising a metal shell with a longitudinal hole in which is housed a metal sheath having one end closed and containing a resistive heating element consisting of an SiC powder, which may also contain a metal powder or a powder of an electrically conductive metal oxide. An electrical terminal has one end that extends up to the vicinity of the closed end of the metal sheath and is inserted inside the resistive element consisting of conductive powders. The terminal is surrounded by an insulating powder set on top of the heating element.
Starting from the above state of the art, the purpose of the present invention is to provide a glow plug with a resistive heating element consisting of conductive powders which makes it possible to vary in a simple way the design value of the resistance of the conductive powders and to obtain a spatial distribution of the resistance inside the metal sheath that is adequate for achieving the desired thermoelectric characteristics, such as position of ignition point, pre-heating time, current absorption, and the like.
According to the present invention the above purpose is achieved by a glow plug having the characteristics that form the subject of the invention